Fuel injector depressor tool

ABSTRACT

Disclosed is a lever type tool for depressing the fuel injector plungers of a diesel engine to test the engine for cylinder misfiring. Change in engine sound after depression of the plunger denotes a properly firing cylinder. Lack of change in engine sound denotes an improperly firing cylinder. The plungerdepressing tool is formed with a hook which is adapted to partially encircle the mounting shaft for an injector rocker arm, whereby the tool is enabled to be swung about the rocker arm pivot axis without slipping out of position. The plunger-engaging surface of the tool is an arcuate surface having a radius of curvature that causes the tool to continually engage the plunger at points near a central radial plane of the plunger.

United States Patent [191 Carpio et al.

[ Mar. 25, 1975 FUEL INJECTOR DEPRESSOR TOOL Tex. 77907 [22] Filed: Mar. 13, 1974 [21] Appl. No.: 450,716

[52] 11.8. C1. 254/131, 29/219 [51] Int. Cl B661 15/00 [58] Field of Search 254/l31.5, 131; 29/267, 29/219; 81/3 R; 145/1 A, 1 B

[56] References Cited UNITED STATES PATENTS 1,923,770 8/1933 Baker 254/131 2,135,065 11/1938 Wick t 254/131 2,540,388 2/1951 Dreeben 254/131 FOREIGN PATENTS OR APPLICATIONS 121,719 7/1946 Australia 254/131 758,324 11/1933 France 254/131 Primary Examiner-Al Lawrence Smith Assistant Examiner-Roscoe V. Parker, Jr.

Attorney, Agent, or Firm1ohn E. McRae; Robert P. Gibson; Nathan Edelberg [57] ABSTRACT Disclosed is a lever type tool for depressing the fuel injector plungers of a diesel engine to test the engine for cylinder misfiring. Change in engine sound after depression of the plunger denotes a properly firing cylinder. Lack of change in engine sound denotes an improperly firing cylinder. The plunger-depressing tool is formed with a hook which is adapted to partially encircle the mounting shaft for an injector rocker arm, whereby the tool is enabled to be swung about the rocker arm pivot axis without slipping out of position. The plunger-engaging surface of the tool is an arcuate surface having a radius of curvature that causes the tool to continually engage the plunger at points near a central radial plane of the plunger.

10 Claims, 2 Drawing Figures FUEL INJECTOR DEPRESSOR TOOL The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without payment to us of any royalty thereon.

BACKGROUND OF THE INVENTION To check the cylinders of diesel engines for misfiring it is a common practice for the mechanic to manually depress individual ones of the fuel injector plungers while the engine is running at an idle speed approximating 500 rpm. If a cylinder is misfiring there will be no noticeable difference in the sound of operation when the respective fuel injector plunger is manually depressed as compared to when it is not. If the cylinder is properly firing there will be a change in engine sound after the associated plunger is manually depressed. Manual depression of the plunger interrupts the fuel pumping operation and thus the combustion process in the associated cylinder.

It is a common practice to depress the fuel injector plungers by placing a screw driver against the end face of the plunger and forcing it down against the plunger spring return force. This practice is dangerous because the engine is running, and the plunger is reciprocating. The screwdriver is apt to slip off the flat end surface of the plunger, thereby causing possible injury to the mechanic and/or damage to fuel lines located alongside the plunger.

THE INVENTION The present invention proposes a lever type tool that can be temporarily hooked onto a part of the engine to provide a stable fulcrum for manual depression of the tool against the end face of each fuel injector plunger. The hook portion of the tool is adapted to partially encircle the mounting shaft for an injector rocker arm to prevent slippage of the tool from its designated location aligned with the injectorplunger.

THE DRAWINGS FIG. 1 is a fragmentary side elevational view of a tool incorporating the invention. The tool is shown in various positions of adjustment relative to a diesel engine.

FIG. 2 is a fragmentary top plan view of the structures shown in FIG. 1. v

The engine can be a conventional diesel engine, as for example an eight cylinder engine manufactured by General Motors Corporation under its designation V-71. Each cylinder of the engine is supplied with diesel fuel by means of a fuel injector which includes an injector plunger 12 slidably mounted for up-anddown motion in timed relation to the associated engine cylinders.

Each plunger 12 is moved downwardly by means of a rocker arm 14 that is rotatably mounted on a shaft 16 that extends through annular collars 17 formed integrally with support pedestals l9; bolts 21 lock the shaft in place. Collars 17 serve as shaft 16 enlargements for properly spacing the various rocker arms. An enginedriven push rod 18 produces rocking movement of the associated arm 14 around the shaft 16 axis. Right end 20 of the rocker arm engages the flat face 22 of plunger 12, whereby upward movement of push rod 18 produces downward-movement of plunger 12. During reverse downward movement of the push rod the plunger is forced upwardly by a compression spring 24 trained between the injector pump housing and the plunger flange 26.

As seen in FIG. 2, the plunger depresser tool 28 comprises a generally U-shaped fork structure 29 engageable with the engine, and a rod-like handle structure 32 extending from the fork structure for manual manipulation by the mechanic. Fork structure 29 includes two similarly configured legs 30 adapted to straddle rocker arm 14. Each leg is curved into the serpentine shape shown in FIG. 1.

The leftmost portions of the fork structure define an arcuate hook means 34 designed to partially encircle and underlie the fixed shaft elements 17. The rightmost portions of the fork structure define an arcuate presser means 36 that aligns with plunger 12. When handle 32 is moved from the full line position 320 to the dotted line position 32b presser means 36 is moved downwardly to exert pressure on plunger 12. Handle 32 will normally be held in its down" position 32b long enough for the mechanic to note any change in engine noise caused by manual depression of the plunger. The tool will then be withdrawn from the particular plunger and repositioned over the next plunger, and so on.

The hook-like structures 34 are internally curved to engage the undersurface of each shaft collar 17 for an arcuate distance a that measures approximately 165 taken around the shaft 16 axis. The arrangement enables the tool to be manually rotated around the shaft 16 axis without inadvertantly disengaging the tool from theengine; the surfaces of collars 17 serve as fulcrum surfaces for effecting lever-like movement of the tool about the shaft 16 axis when manual pressure is applied to handle 32. When the handle is moved from position 32a to position 32b the plunger 12 is depressed through the stroke designated by numeral 33. With a sufficiently long handle the tool can be readily held in the down position against the force of spring 24.

The engine usually has a relatively small clearance space between the rocker arm shaft and the fuel injector plungers. For example, in one illustrative engine the shaft central plane 43 is spaced laterally from the plunger central plane 45 by a distance 0 that measures approximately 1% inches. The relatively small clearance space requires that the tool be initially installed on the engine in a slightly overturned" condition as denoted by numeral 46.

With the engine running at normal idling speed the overturned tool can be advanced leftwardly to cause the toe portions 48 of hook structures 34 to move underneath shaft collars 17; such movement positions the hump sections 50 of the fork structure against upper surface areas of the shaft collars. The tool can then be pivoted clockwise to its use position shown in full lines in FIG. 1. Removal of the tool can be accomplished in a reverse procedure; i.e., by pivoting the tool counterclockwise to the overturned position, and then withdrawing it to the right. The engine can be kept running throughout the tool-installing and toolremoving periods.

Hook structures 34 are dimensioned to partially encircle shaft collars 17 through an arcuate distance a of at least degrees, and preferably about as shown in FIG. 1. The shaft-encircling hook structures 34 have sufficient circumferential dimensions to prevent lateral slippage of the tool (either to the right or to the left) while the tool is in use. Presser structures 36 engage plunger surface 22 to prevent downward slippage of the tool. The two structures 34 and 36 cooperatively prevent lateral and downward slippage of the tool.

When the tool is in use an imaginary plane 43 bisects" the hook means 34; i.e., the curved hook surface extend approximately the same arcuate distance on eith'er side of plane 43. An imaginary force line drawn from plunger surface 22 to point 41 on the curved surface of hook means 34 is at right angles to the bisecting plane 43. Such an imaginary force line represents the direction of the lateral forces tending to produce slippage of the tool from the rocker arm shaft 16. Hook means 34 is oriented or configured to resist movement of the tool in such lateral directions.

The lower convex surface of presser means 30 is centered on an imaginary axis 31 extending parallel to the axis of shaft 16. The radius of curvature of this convex presser surface is slightly less than the diameter of plunger 12, and approximately one third the effective length of the lever'arm measured from the axis of shaft 16 (dimension C). With such dimensional relationships the presser surface enjoys a relatively slight shift or play on plunger surface 22 during the plunger depression stroke. At the beginning of the downstroke presser means 30 engages the plunger surface 22 at points in the imaginary plane designated by numeral 47. At conclusion of the downstroke presser means 30 engages the plunger surface 22 at points in the imaginary plane designated by numeral 48. The distance between planes 47 and 48 represents the shift of the presser means on surface 22 during the plunger downstroke.

The relatively slight shift ofpresser means 30 along plunger surface 22 insures that presser means 30 engages surface 22 at points near the plunger longitudinal centerline 45 during the entire downstroke of the tool. Asv shown in FIG. 2, the presser means contacts the plunger at outer segmental areas of surface 22. The relatively slight shift of the presser means along the plunger surface assures proper contact location sufficient contact area even though the segmental areas are relatively small.

For the particular engine shown in the drawings the tool should, as a practical matter, be designed so that the bisecting plane 43 through hook means 34 is at right angles to an imaginary line interconnecting the centers of curvature 29 and 31 of the two arcuate mechanisms 34 and 36. This appears to provide a proper geometrical relationship between the various arcuate mechanisms.

The radius of curvature of the convex surface on presser section 36 is preferably approximately one third the length of the lever arm measured from the axis of shaft 16. The radius of curvature of the presser section surface works out to be slightly less than the radius of curvature of the concave surface on hook means 34 when the tool is designed for use on the illustrated engine.

The tool can be made economically and sufficiently rigid if the fork structure 29 is formed from a single length of square or rectangular bar stock, and then welded or otherwise connected to handle 32. The bar can initially be bent into a U configuration, as seen in FIG.2, and then bent into the serpentine shape shown in H6. 1. Theflat surface areas of the rectangular stock increase the surface areas in contact with the engine surfaces and thus reduced unit area loadings.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

We claim:

1. A fuel injector depresser tool comprising arcuate hook means adapted to partially encircle a fuel injector rocker arm shaft to temporarily mount the tool for arcuate motion around the shaft axis; presser means having a surface adapted to engage the end face of a fuel injector plunger for depressing same to the cylinder misfire position, and a manually operated handle for effecting arcuate movement of the tool around the shaft axis; said hook means having an arcuate shaftengagement surface measuring at least approximately around the shaft axis for preventing inadvertant shifting of the tool relative to the shaft when the presser means is engaged with the plunger.

2. The tool of claim 1 wherein the plungerengagement surface is an arcuate surface centered on an imaginary axis parallel to the axis defined by the aforementioned shaft-engagement surface; an imaginary bisect plane taken through the arcuate shaftengagement surface being perpendicular to a line interconnecting the two axes.

3. The tool of claim 2 wherein the radius of curvature of the plunger-engagement surface is approximately one third the length of the lever arm measured from the rocker arm shaft axis to the plunger-engagement surface.

4. The tool of claim 1 wherein the hook means and presser means define a structure having a serpentine shape.

5. The tool of claim 4 wherein the presser means has a lesser radius of curvature than the hook means.

6. The tool of claim 1 wherein the hook means and presser means are formed from bar stockinto a serpentine configuration.

7. The tool of claim 1 wherein the plungerengagement surface is an arcuate surface having a radius of curvature slightly less than the radius of curvature of the shaft-engagement surface.

8. The tool of claim 1 wherein the shaft-engagement surface and plunger-engagement surface are oppositely directed to exert oppositely acting forces on the shaft and plunger.

9. The tool of claim 1 wherein the hook means and presser means are constructed as a fork structure adapted to straddle the rocker arm of the engine.

10. The tool of claim 9 wherein the fork structure is formed from a single length of rectangular bar stock. 

1. A fuel injector depresser tool comprising arcuate hook means adapted to partially encircle a fuel injector rocker arm shaft to temporarily mount the tool for arcuate motion around the shaft axis; presser means having a surface adapted to engage the end face of a fUel injector plunger for depressing same to the cylinder misfire position, and a manually operated handle for effecting arcuate movement of the tool around the shaft axis; said hook means having an arcuate shaft-engagement surface measuring at least approximately 150* around the shaft axis for preventing inadvertant shifting of the tool relative to the shaft when the presser means is engaged with the plunger.
 2. The tool of claim 1 wherein the plunger-engagement surface is an arcuate surface centered on an imaginary axis parallel to the axis defined by the aforementioned shaft-engagement surface; an imaginary bisect plane taken through the arcuate shaft-engagement surface being perpendicular to a line interconnecting the two axes.
 3. The tool of claim 2 wherein the radius of curvature of the plunger-engagement surface is approximately one third the length of the lever arm measured from the rocker arm shaft axis to the plunger-engagement surface.
 4. The tool of claim 1 wherein the hook means and presser means define a structure having a serpentine shape.
 5. The tool of claim 4 wherein the presser means has a lesser radius of curvature than the hook means.
 6. The tool of claim 1 wherein the hook means and presser means are formed from bar stock into a serpentine configuration.
 7. The tool of claim 1 wherein the plunger-engagement surface is an arcuate surface having a radius of curvature slightly less than the radius of curvature of the shaft-engagement surface.
 8. The tool of claim 1 wherein the shaft-engagement surface and plunger-engagement surface are oppositely directed to exert oppositely acting forces on the shaft and plunger.
 9. The tool of claim 1 wherein the hook means and presser means are constructed as a fork structure adapted to straddle the rocker arm of the engine.
 10. The tool of claim 9 wherein the fork structure is formed from a single length of rectangular bar stock. 